Calibrated injection pump



Dec. 15, 1959 c. A. MILLER 2,916,998

CALIBRATED INJECTION PUMP Filed June v6, 1956 2 Sheets-Sheet 1 2 IOc -Z- 2kA T nr lNVENTOR Curl A. MiHer BY Dec. 15, 1959 c. A. MILLER 2,915,998

CALIBRATED INJECTION PUMP Filed June 6, 1956 2 Sheets-Sheet 2 mh 1E E CALDERATED INJECTION P Carl A. Miller, White Bear, Minn., assignor to Economics Laboratory, linc., St. Paul, Minn., a corporation of elaware Application lune 6, 1956, Serial No. 539,776

20 Claims. (Cl. 10S-3S) This invention relates to reciprocating pumps and especially to those of the injector type of which the capacity can be accurately controlled and, preferably, calibrated.

Pumps for injecting a liquid into a chamber or into another liquid in measured quantities have heretofore been proposed in various forms, but most of them are of complicated, expensive construction, or are unreliable when of small capacity. As far as I am aware, none meets the primary object of the present invention which is to inject extremely small quantities of one liquid into another liquid which is flowing under pressure, and with high relative volumetric accuracy even when operating intermittently.

The pump according to the present invention may take any of several different forms, but, in general, it comprises a cylinder block containing at least two intersecting bores preferably at right angles to each other, one of which constitutes the cylinder. The remaining bore or bores constitute the inlet and outlet for the cylinder. Suitable check valves are included in the inlet and outlet bores, where required. 'l'hese check valves are preferably of the ball type of which the valve seat is an O-ring of resilient material. A stra1ght piston is provided to reciprocate in the cylinder and, according to the invention, the seal between the piston and the cylinder wall is provided by one or more rings of resilient material. Preferably the outlet valve is adapted to be opened by physical contact with the piston at the top of its stroke. In order to enhance the accuracy of the volumetric capacity and to simplify the construction further, the connecting rod by which the piston is reciprocated is constructed of resilient material and has no bearings. Since substantially the only parts subject to wear are the mentioned O-rings which are readily replaceable, servicing of the pump is easy and inexpensive, and the pump itself has an unusually long life.

The invention also includes means for accurately adjusting the capacity per stroke. For this purpose I prefer to employ a piston stroke of constant length and to vary the pump capacity by selecting the proportion of the part of the cylinder length traversed by the piston head per stroke to the total length of the piston stroke.

An important advantage of the pump according to the invention is that it is self-purging of air and, therefore, selfstarting and accurate. Heretofore it has been a great problem to design pumps of very small capacity which were self-purging. However, the self-purging pump as herein described can be made in very small sizes, for example of a capacity as low as of the order of .00014 cu. inch'per stroke, or less.

The above-mentioned features and advantages of the invention, in addition to many others, will be better understood from the following description considered in connection with the accompanying drawings in which:

Fig. 1 is a side elevation of a complete assembly of injector pump driven by a water-meter motor according to the invention;

2,916,998 Patented Dec. 1.5, 1959 ice Fig. 2 is a plan view of the assembly of Fig. l;

Fig. 3 is a. sectional-view of a preferred embodiment of pump according to the invention showing the piston in the central part of its down stroke;

Fig. 3A is a fragmentary view of the embodiment of Fig. 3 showing the piston approaching the top of its up stroke;

Fig. 4 is a sectional view of the capacity-adjusting means shown in Figs. 1 and 2;

Fig. 5 illustrates a modified embodiment of the invention, including certain of the features of the pump of Fig. 3;

Fig. 6 shows a modified form of adjustable-capacity pump; and

Fig. 7 illustrates another embodiment which is of the double-acting type.

Figs. 1 and 2 illustrate a preferred embodiment of my injector pump which is mounted on the casing of a watermeter motor by which it is driven. The pump here illustrated is adapted to inject a concentrated liquid into a moving water stream with high relative volumetric accuracy. Since the pump is driven by a water-meter motor powered by the water stream the operation of the pump is automatically maintained proportional to the rate of ow of the stream. By injecting the liquid into the water stream at the inlet side of the water motor., the turbulence induced by the motor automatically provides thorough mixing of the two liquids before they are discharged at the outlet side of the motor casing.

The specific object of the assembly illustrated in Figs. 1 and 2 is to inject into a stream of hot water, a liquid which decreases the surface tension and therefore increases the wetting properties of the water. The device has been employed with considerable success in connection with dishwashing machines in which the rinse water can thus be treated to minimize visible spotting of dishes, glassware and silverware as the result of mineral deposits from the water upon drying. In this particular application it is required that the injected liquid be: mixed with the water in a proportion of approximately 200 parts per million or less, and that this proportion be maintained regardless of the rate of water ow. Hence it is necessary that the capacity of the pump be adjustable to a desired value which will thereafter remain substantially constant from zero to the maximum low rate of the water. It is also required that this proportion be maintained in spite of the fact that the pressure of the water stream is usually variable and commonly is as high as lbs. per sq. inch. However, the pump will operate against pressures considerably greater than this. The invention obviously is suited to many other applications, of which an important one is fuel injection' in internal combustion engines.

Because of the extremely small dimensions of the cornponent parts of a pump in which the capacity is adjustable between zero and .00114 cu. inch per stroke, for example. the pump of the present invention includes constructional features which depart materially from conventional pump design. However, it appears that many of the features of the invention are likewise applicable and similarly useful in pumps of larger dimensions and pumping capacity. Therefore, several modifications of the preferred embodiment are herein described as additional examples of the invention.

Referring rst to Figs. 1 and 2, a water motor 1 of the water-meter type is shown to have a water inlet 2 and a water outlet 3. Water meter motors of the Calmet, Hersey and Badger types are suitable. On the cover plate 4 of the water motor is mounted a bracket 5 which supports the pump, an eccentric cam by which the pump is driven, and the connecting rod mechanism by which the pump capacity may be adjusted.

As seen in the drawing, the pump is of small dimensions, and comprises essentially a cylinder block 6 in which a piston 7 reciprocates. To the bottom end of the piston a connecting rod4 S is rigidly secured, as by brazing. The `other end of the connecting rod S Vis similarly secured to Vthe capacity-adjusting device 9 which will be described in more detail in connection with Fig. 4., In effect, device 9 changes the length of the piston rod without changing the length of its stroke. Since connecting rod 8 is bearingless and yet must impart to the piston a reciprocating motion derived from the rotary motion of a driving shaft, this connecting rod is composed of flexible, resilient material having driving strength in both compression andv tension. A suitable material is piano wire, stainless steel being preferable. In. the,particula'r embodiment here illustrated, wire of .028" diameter, or slightly less, was found to be satisfactory. By eliminating piston rod and connecting rod bearings, not only the usual frictional losses, but also inaccuracies dueto wear and lost motion, are avoided.

Yertical shaft 10, which is rotated by the water motor l-,ni/,S round where it passes through the cover-plate 4 and through adjacentbracket but the upper portion 10a is of hexagonal cross-section, as seen more clearly in Fig. 2. The eccentric cam 11 includes an eccentric disc, or driving member, 12a through which the hexagonal shaft a passes and which is rotated thereby. Ffhe eccentricstrp, 0r driven member, 12. is secured to boss 39 whhd'n turn, is attached through threaded rod 37 toconnectng rodtt, as shown in Fig. 4.

V "lfhe inlet pipe 13 supplies the desired liquid from a suitable reservoir (not shown), to the inlet side of the pump. It is desirable, but not necessary, that the reservoir bevabove the pump because the pump creates app reciable suction, and its accuracy is independent of the pressure head of the liquid being pumped. A. check valve is included in this inlet line and preferably is located"withinwthevblock 6 close to the cylinder. It is sometimesdesirable to bring this inlet into the top of thek block instead of into therbottom, especially if any diculty is experienced as a result of formation of an air pocket.v The. outlet pipe 14 couples the output or exhaust eind of the cylinder to the inlet side 2 of the water motor casing. As later described, an outlet check valve of novel form is located within the pump itself.

In applications of the type herein described by way of example, it is necessary to eliminate time lag in respect to the commencement of fluid injection when the pump, beginsrto operate, and in respect to injected fluid cut-olf when the vpump ceases to operate. However, since the quantity pumped is so minute, the pipe 14 requires an appreciable time to lill. Also, if it were full at the instant when cutoff should occur most of the liquid in the pipe can empty into the water stream after the injectionushould have ceased. Finally, water should not back up into the liquid feed line 14 because this would interfere with the accuracy of the control of the quantity of injected liquid. It is therefore Vimportant that a check valve 15 be inserted where the line 14 enters the casing ofthewater'motor and that it be of a type which opens and closes rapidly and which discharges immediately into thewater stream within the casing without interposition of chambers or passages. A novel check valve having the above-mentioned advantages is described in my copending U.S. lpatent application Serial No. 586,176, filed Mayk 21, 19576.

The preferred embodiment of the resented generally in Figs. 1 and 2, tail in Figi. 3v. It comprisespa cylinder block 6 into which two bores are drilled atv right angles. The first bore passes through the block from one end to the other and is of two diameters,lthe smaller comprising the cylinder 1,6 vand the Vlarger comprising the two outside portions 17 and 18 on either end of thesmall bore portion. The second bore 19 is drilled into the block from the bottom.

pump which is repis illustrated in de- (or top) so as to open into the cylinder 16 near the shoulder 20 which forms the junction between the smaller bore 16 and tne larger bore 17. Bore 19 comprises the inlet, bore 17 the outlet, and bore 18 accommodates the piston.

A metal plug 21 is screwed into suitable threads in the wall of bore 18. Through the center of this plug a hole 22 is drilled which has the same diameter as that of cylinder 16, being approximately .006" larger than the piston sol as to function as a piston guide bearing. Plug 21 is sealed in bore 18 by means of the small synthetic rubber O-ring 23 which is carried in a suitable groove near the end of the plug. Between this end of plug 21 and shoulder 24 a larger O-ring 25, of similar material, is slightly compressed. The diameter of the central hole in this O-ring is slightly smaller than the diameter of the piston 7 which slides through it with a sealed fit.

The inlet connector plug 26 is threaded into the bore 19 and is sealed therein by another small O-ring 27. The larger 0-ring 28 provides a seat for the inlet check valve ball 29. yOn the exterior end of plug 26 screw threads are provided to accommodate the coupling nut 30.

The bore 17 is threaded to accommodate an outlet connector plug 31 which, like the other two plugs, is sealed in place by small O-ring 32. The larger O-ring 33 provides a seat for the outlet valve ball34 which is retained in closed position by spring 35. The central hole in O-ring 3 3 is of the same diameter as that of O-ring 25 to provide a` sealed fit with the piston.

Several advantages result from employing O-rings as here illustrated and described. In the past it has been customary to secure the piston rings to the piston so that they slide in the cylinder with a sealed fit against the cylinder wall. In the present invention this practice has not been followed. instead, the piston rings are stationary and the straight, smooth piston is arranged to reciprocate through the central hole in the resilient ring with which it forms a seal. This avoids wear of the cylinder wall, permits the use of a piston of unusually small diameter, and permits use of a piston ring considerably larger, stronger, and of longer life than would be the case if thering were seated in a groove formed in the piston itself. Furthermore, a groove in a piston of such small ldiameter as herein employed would greatly weaken the piston, inviting bending and breakage. This fact is readily understood when it is realized that the piston herein illustrated had a diameter of between .06 and .07 inch.

Since the cylinder block 6 of the pump is subject tosuch slight wear, it may be made of any of many different materials, of which metals and plastics are examples. In the illustrated embodiment the cylinder block was cut 11/8 inches long from a 11/2 inch diameter round rod of Iclear polymerized methyl methacrylate, known commerically as Plexiglas After two flat parallel surfaces were formed on this block to comprise the top and bottom, the necessary bores were Vdrilled in it as above described. Blocks cut from rectangular stock would obviously require less machining. It will be evident that the pumps as herein described are of simple and inexpensive construction and require a minimum of precision machining notwithstanding the fact that they are precision pumps.

As mentioned above, the pump as illustrated in Figs.

3 and 3A, is preferably operated with a piston stroke of constant length. The capacity of the pump is adjusted by changing the proportion of the part of the cylinder length which the head portion of the piston Vtraverses to the total piston stroke. In Fig. 3 the piston is shown on its down stroke during which valve 29 is open and valve 34 'is closed. rihs draws fluid into cylinder 16 through inlet pipe Tg3. The piston, at ail positions of its stroke, is sealed by O-ring 25. On its up or compression stroke the liquid in the cylinder 16 is compressed and,

as the pressure increases, the outlet valve 34 opens against the pressure of spring 35. However, should a small quantity of air be entrapped in the head of cylinder 16 (as when starting the pump), this air will compress, and the resulting pressure may not be sufficient to open valve 34. This condition exists in some prior pumps, and prevents purging and self-priming. However, in accordance with the present invention, the piston stroke is such that when the piston 7 contacts ball 34 it does not stop, but continues its stroke as shown in Fig. 3A, until it physically moves the ball into open position. For this reason the piston head is formed with a concave surface 36 of the same radius as ball 34. By thus mechanically opening the outlet valve at the top of its stroke, the piston automatically expels any air which may have been entrapped in the cylinder and permits the liquid to replace it. In normal operation when pumping liquids, the head of the piston during the compression stroke does not contact the ball because the liquid retained in the depression or cup at the piston head separates the two metal surfaces. On the return stroke of the piston the valve ball 34, which, as shown, is larger than the diameter of the piston, follows the piston until it seats on O-ring 33, closing the outlet valve before the head of the piston has been withdrawn from its sealed relation with the O-ring 33. Consequently, at one phase of the piston return stroke, the piston head is sealed in the O-ring at the same time that the outlet valve is closed. Also the cylinder is sealed from the pump outlet in all phases of operation except when the pumped fluid is being expelled from the cylinder under pressure.

Consideration of the construction illustrated in Figs. 3 and 3A will disclose that the effective cylinder length comprises the longitudinal distance between O-rings 25 and 33. It will also be noted that the portion of the piston stroke which occurs while the piston is sealed in O-ring 33 is not related to the pump capacity. In other words, if the piston head reaches the O-ring 25 at the bottom of the piston stroke the pump will have maximum pumping capacity; whereas if the entire piston stroke occurs to the left of O-ring 33, the pump will have zero pumping capacity. Hence it follows that the pumping capacity can be adjusted from zero to maximum by changing the proportion of the length of the stroke of the piston head which occurs on each side of the cylinderhead O-ring 33.

The adjustment of the pump capacity just described can be effected by changing the effective length of the connecting rod between the piston and the crank shaft, or the equivalent, while maintaining the length of the stroke constant. ln the embodiment herein shown this change of length of the connecting rod can be readily made by the manual adjusting device illustrated in Figs. l, 2 and 4. This device comprises a threaded stud 37 to which one end of the flexible connecting rod 8 is brazed. This stud screws into a threaded hole 33 in boss 39 which forms a part of the driven member 12 of the eccentric cam. Thus by rotating the piston 7 and stud 37 in one direction or the other, the piston rod may be shortened or lengthened. The knurled cap 40 is also threaded to stud 37 and carries peripheral graduations, or an index, which can be read against linear calibration marks along the surface of boss 39, in the manner illustrated in Fig. 2. To provide a frictional bearing surface for the open end of cap 40, a rubber O-ring dll is secured in a groove near the end of boss 39. A lock nut 42, when drawn tight against the head of cap 40, locks the cap to the threaded rod 37 so that the rotation of cap 40 causes stud 37 and piston 7 to rotate with it.

In practice, device 9 is adjusted by loosening lock nut 42 and turning the piston until it assumes the longitudinal position in the cylinder which is to be considered as zerof This may be a mid-range point, for example. Then, while the piston is held against rotation, cap 40 is turned until the zero mark, or some other calibration coincides with the index on the cap. Lock nut 42 is. then tightened against the head of the cap. Thereafter, manual rotation of the cap itl will adjust the position of the piston in the cylinder, and hence the pumping capacity within an extremely close tolerance. The calibrations may, of course, be empirically predetermined in terms of thousandths of a cubic centimeter, cubic inch, or any other desired pump capacity unit.

in the remaining figures, three alternative embodiments of the invention are illustrated. To simplify the drawings, the embodiments of Fig. 5, Fig. 6 and Fig. 7 are shown without screw threads, sealing rings and other details which should be obvious from consideration of Fig. 3.

The construction of the pump illustrated in Fig. 5 is extremely simple, but it includes some of the features and advantages of the pump shown in Fig. 3. As before, it comprises a cylinder block 42 in which two intersecting bores are drilled. The first bore, which passes through the block, encloses the inlet and outlet valves, whereas the second bore constitutes the cylinder and does not pass completely through the block, but intersects the first bore away from the top end. Here, the inlet and outlet check valves 43 and 44 are located in the cylinder block as close as possible to the cylinder 45. (In practice they should be closer than is apparent in the drawing.) This reduces to a negligible amount the volume of air which can accumulate at the outlet. lu this embodiment the outlet valve is not mechanically opened by the piston as it is in Fig. 3. The pump illustrated in Fig. 5 has been demonstrated to be self-purging because insufficient volume of air to form a lock can accumulate, especially if the outlet port and valve are disposed on the top of the cylinder, as shown.

The capacity of the pump of Fig. 5 can be varied by adjusting the length of the piston stroke instead of, or-

in combination with means for adjusting the position of the stroke in the cylinder. Mechanisms for adjusting the length of piston stroke have been known for many years.

One o-f the earlier forms is described in U.S. Patent No. 976,148 to J. E. Caps.

The pump illustrated in Fig. 6 includes s-everal novel features, some of which are similar to those of the embodiment of Fig. 3. This pump is self-purging for the reasons mentioned in connection with Fig. 5, and can be constructed to provide very small pumping capacity. The pump of Fig. 6 includes a novel feature which is not included in the other embodiments, namely, that the pump itself incorporates means by which the pump capacit-y can be altered or adjusted independently of the length of the connecting rod and of the length of the stroke.

This pump comprises a cylinder block i6 through which a single bore is drilled from one side to the other, as shown. The central part of this bore forms the cylinder 47. The right-hand end of the bore is closed, as in Fig. 3, by a piston-guide plug 48, and the left-hand end is closed with a cylinder-head plug 49. An inlet port 5d communicates with the cylinder head passage 51. A check valve is not included in the inlet port 5G for the reason below explained. The outlet port S2 corresponds to that of Fig. 5, and includes an outlet check valve 53, which may be assumed to be of the same construction as that of Fig. 5.

The principal advantage of the pump of Fig. 6 resides in the novel construction of the piston and in its relation to the remainder of the pump. As seen in the drawing, the diameter of the piston 54 is suicient to receive a threaded stud 55' which is integral with the piston-head extension 56. The diameter of the hole in the center of cylinder head O-ring S7 is such as to form a seal with the extension piece 56. O-ring S8 corresponds in its function to O-ring 25 of Fig. 3.

Piston head 59 is effective in the pumping action. Piston-head extension 56, in cooperation with O-ring 57, serves in the combined capacity of an inlet valve and of means for adjusting the capacity of the pump. As the pistonrnoves to the right on its down stroke the extension piece 56 is withdrawn from O-ring 57. Thus, as cylinder head 59 continues to move to the richt the volumetric capacity of 'cylinder 47 surrounding er r"on 56, increases, thus drawing liquid through port into the cylinder 47. The bottom of the stroke occurs while piston 54 is still sealed in O-rinG 58. After the piston reverses, starting its upstrolie, liquid is pushed buck through O-ring 57 and into port 5t), but as soon tension piece 56 seals itself within G-ring S7, the re in the cylinder rapidly increases, forcing the liquid through valve S3 and from outlet port 52. From this it is apparent that the pump capacity depends upc length of the piston extension piece 56 as treasure piston head 59.

The capacity of the pump of Fig. 6 can, as above explained, be adjusted either by screwing extension piece 56 in or out of the piston S4, or by substituting an extension piece of different length. ln either change can be made by removing plug 49 and turning the extension piece 56 with a small screw driver. Usually it is preferable to make the desired change by substituting extension pieces, although, if the screw threads are snificiently tight a reasonable degree of adjustment satisfactorily achieved merely by turning the ext piece in either direction, as required. in this embodiment, as well as in the others, the pump capacity can also be adjusted by changing the length of the piston stroke.

The modification illustrated in Fig. 7 comprises a double-acting pump which incorporates of the features of the invention above described. Being of doubleacting type, this pump provides two exhaust or outlet pulses per rotation of the shaft of the driving motor, thus producing smooth pump action. in spite of the facts that this pump is double-acting and that the diameter of the piston should be greater than in the other embodiments, the pumping capacity need not be greater, because the capacity is determined by the relative diameters of the piston and the cylinder. Since the piston ring is secured in a groove in the piston, the diameter of the piston should be slightly greater than the diameters of the pistons shown in Figs. 3 and 5, for example. if it is not feasible to cut a groove around the piston, the piston ring can be held in a channel formed on the surface of the piston, as by brazing two parallel rings spaced apart on the surface of the piston, or by machining tbem on a single bar of metal.

The pump of Fig. 7 comprises, as before, a cylinder block 60 through which a cylinder 61 is bored. A piston guide plug 62 is inserted in one end of the bore so as to hold the O-ring 63 which corresponds to O-ring 25 of Fig. 3. A corresponding plug could be employed in the opposite end of the block, if desired, but it has been found that the simpler construction as illustrated is satisfactory. This comprises a groove 64 cut directly in the cylinder block -into which another O-ring 65 is inserted.

Each of inlet valves V66 and 67 comprises a springpressed ball seated against a small O-ring which is secured in a groove cut in the cylinder block, as shown. This is a very simple construction and has proved to be satisfactory. However, if preferred, a coupling plug, such as plug 26 of Fig. 3 depending on the nature of the inlet pipe, may be used.

Outlet valves 68 and 69 could be held in by plugs as in Fig. and Fig. 6, but the construction illustrated in Fig'. 7 is a satisfactory alternative. Here, each valve spring is retained by a severed rubber O-ring 70 and 7l which can readily be snapped into its groove in the cylinder block after the three parts of the valve have been placed in position. Y

The piston illustrated in Fig. 7, is easily assembled in the pump as follows: First, O-ring 63 is inserted and the plug i62 -screwedtinto the position. Then thetpiston 0- 8 ring 72 is placed on the piston 76 and the piston inserted from the left (in the drawing) through O-,ring 63 and guide 62. The piston 76 is then moved as far as it will go to the right, at which point the left-hand end of the piston will be inside of the groove 64. O-ring can then readily be slipped into its groove 64, and the piston pushed to the left so that it passes through the center hole in O-ring 65. Y

The construction of this pump limits the maximum length of the piston stroke to the distance between the inlet ports 74 and 7S longitudinally of the cylinder, which is the same as the distance between the corresponding outlet ports immediately above them. The pumping capacity can be readily adjusted by varying the length ofthe piston stroke up to this maximum. such adjustable driving means Vare known in the art.

Since, in the embodiment of Fig. 7, the piston ring 72 is in frictional contact with the cylinder wall, there must be some wear on the cylinder wall as well as on the piston ring. However, in the embodiments of the doubleacting pump heretofore constructed no detectable wear ias been observed on the Plexiglas block. Although metal may be employed for this element, the ability to observe the operation of all of the components of the pump while in use has proved a valuable advantage of the plastic material.

I claim:

l. A pump comprising a cylinder block having a first bore extending into the block from one side thereof, one portion of said bore being of larger diameter than the other portion so as to form a first shoulder therebetween, a Asecond bore extending from another side of the block and terminating in the smaller portion of said first bore, said second bore comprising an inner part and an outer part of which the outer part is of larger diameter than the inner part so as to form a second shoulder therebetween, a piston fitted to reciprocate in the smaller portion of said first bore, a first O-ring of resilient material positioned against vsaid first shoulder, the diameter of the aperture in said O-ring being slightly less than vthe diameter of the piston passing through it to form a seal therewith, a first bored plug sealed in the larger end of said first bore and having an annular end which presses said O-ring against said first shoulder, a first 'ball within the bore of said plug and spring means tending to press the ball in symmetrical contact with said O-ring closing the aperture in said O-ring to form a normally closed exhaust valve, a second O-ring of resilient material positioned against said second shoulder, a second bored plug sealed in the outer part of said second bore and having an annular end which presses said second O-ring against said second shoulder, a second ball within the bore of said second plug and second spring means tending to press said second ball in symmetrical Contact with said second O-ring closing the aperture in said second O-ring to form a normally closed inlet valve.

2. A pump according to claim 1 in which the head of said piston is circular and concave and the stroke of the piston carries the piston head through said first O-ring into contact with the ball of said exhaust valve, if closed, so as to move the exhaust valve ball into open position.

3. An injector pump of adjustable capacity which includes a cylinder, a piston disposed to reciprocate therein, inlet and outlet valves ported inV said cylinder, and means for driving said piston in reciprocating movement, including a rotating driving shaft, attachment means connected eccentrically to said shaft, and a flexible, resilient bearingless piston rod connecting said piston to said attachment means, said rod being rigidly secured at one end to said piston, a member rigidly secured to the other end of said rod. securable to said attachment means and adjustable lengthwise of said rod in respect to 'said attachment means, whereby to adjust the position of the travel As above mentioned,

path of the piston in the cylinder and thereby the pump capacity per stroke.

4. An injector pump of adjustable capacity, which includes a cylinder having inlet and outlet ports, stationary piston rings disposed at opposite ends of said cylinder, a piston adapted to reciprocate in the cylinder through said rings, a piston rod for the piston, each piston ring having a central aperture dimensioned to provide a seal with the portion of the piston which passes through it, the linear distance between said rings constituting the cylinder length, a head portion on said piston, and adjustable means for effectively lengthening and shortening said piston rod and thereby changing the proportion of the part or' the cylinder length which said head portion traverses to the total piston stroke, whereby to adjust the pump capacity.

5. An injector pump of adjustable capacity, which includes a cylinder having inlet and outlet ports, stationary piston rings disposed at opposite ends of said cylinder, a piston adapted to reciprocate in the cylinder through said rings, a piston rod for said piston, each piston ring having a central aperture dimensioned to provide a seal with the portion of the piston which passes through it, the linear distance between said rings constituting the cylinder length, a head extension on said piston of smaller cross section than the remainder of the piston, means for driving said piston rod and piston such that at the bottom of the piston stroke the end of said head extension is withdrawn from the ring through which it passes, and adjustable means linking said piston rod and driving means for changing the proportion of the part of the cylinder length which said head extension traverses to the total piston stroke, whereby to adjust the pump capacity.

6. An injector pump of adjustable capacity, which includes a cylinder having inlet and outlet ports, stationary piston rings disposed at opposite ends of said cylinder, a piston comprising a body and a head portion adapted to reciprocate in the cylinder through said rings, said head portion being of smaller cross-section than said body, each piston ring having a central aperture dimensioned to provide a seal with the portion of the piston which passes through it, the ring through which said head portion passes comprising the effective cylinder head, and said piston-head portion and cylinder-head ring together comprising an inlet valve, the linear distance between said rings constituting the cylinder length, means for driving said piston with a constant length of stroke such that at the bottom of the piston stroke said head portion is withdrawn from said cylinder-head ring, and means for changing the proportion of the part of the stroke length of said head portion which occurs on the respective sides of said cylinder-head ring, which comprises means for changing the length of the head portion of said piston whereby t change the separation between the head of the piston and said cylinder head at the bottom of said stroke and thereby to adjust the pump capacity.

7. An injector pump including a -cylinder block, a bore extending through said block between opposite sides thereof and another bore extending from a second side of said block to intersect said first bore near the midsection thereof, a reciprocating piston disposed in a first one of said bores, a first O-ring of resilient material fixed in said first bore and proportioned such that the piston is adapted to reciprocate through said ring in continuous piston-sealing relation therewith, inlet and outlet values connecting with said cylinder, the second of said bores including one of said valves, said last-named valve comprising a second O-ring of resilient material fixed in said second bore, a ball proportioned to seat in the aperture of said second O-ring, and resilient means urging said ball against said second O-ring.

8. ln combination, an injector pump of adjustable capacity adapted to inject measured small quantities of fluid into a liquid stream flowing under pressure in a closed conduit, which includes a cylinder having inlet and outlet ports, stationary piston rings disposed at opposite ends of said cylinder, a piston adapted to reciprocate in the cylinder through said rings, each piston ring having a central aperture dimensioned to provide a seal with the portion of the piston which passes through it, the linear distance between said rings constituting the cylinder length, a head portion on said piston, driving means for said pump comprising a rotating driving shaft, means imparting to said piston a reciprocating motion derived from the rotating motion of said shaft, said last-named means including a piston rod coupled at one end to said piston and at the other end to said driving shaft and means for adjusting the effective length of the piston rod to change the proportion of the part of the cylinder length which said head portion traverses to the total piston stroke whereby to adjust the pump capacity, driving means coupled to said shaft and comprising means automatically varying the rate of rotation of said shaft in proportion to the rate of ow of said liquid stream, an inlet valve in said inlet port, an outlet valve in said outlet port, an inlet pipe connected to the inlet port and adapted to feed fluid into said inlet port, an outlet pipe connecting said outlet port to said conduit and adapted to feed fluid at a measure rate into said liquid stream, said outlet pipe being of volumetric capacity much greater than the maximum capacity of said pump, and a check valve consituting the terminus of said outlet pipe in said conduit, said check valve being of the type which opens into said conduit and which has a valve seat substantially at the extreme outlet end of the valve and thereby within said liquid stream.

9. In an injector pump of precision type including a cylinder, a piston disposed to` reciprocate therein, and a driving member movable in an orbit around a center of rotation, a bearingless piston rod connected to said piston to drive the same, said piston rod comprising a length of flexible, resiiient wire-like material of round crosssection and so proportioned as to provide driving strength in compression and tension sufficient to actuate the piston in its pumping stroke in either direction, said rod being rigidly secured at one end to the piston, extensible means to the rod rigidly secured to the other end thereof and coupled to said driving member, said extensible means being adjustable by rotation of said piston and piston rod to alter the effective length of the piston rod.

lO. An injector pump of precision type which includes a cylinder, a piston disposed to reciprocate therein, said piston being rotatable in the cylinder, inlet and outlet valves ported into said cylinder, a rotating driving shaft, a coupling member driven by said shaft in an orbital motion, and means including said member which imparts to said piston a reciprocating motion, said means including a bearingless piston rod of exible, straight wire having substantially equal resiliency in all radial directions and being rigidly affixed at one end to said piston and rigidly ah'ixed at the other end to said coupling member, said wire being of material having driving strength in compression sufficient to actuate the piston in its pumping stroke and being of diameter of the order of one-half that of the piston.

1l. An injector pump including a cylinder block, a first bore extending through said block between opposite sides thereof and a second bore extending from another side of said block and terminating in said first bore near the midsection thereof, said bores having enlarged portions at their outer ends to form shoulders with the walls of the inner portions thereof, a reciprocating piston disposed in said second bore, a first O-ring of resilient material disposed against the shoulder in said second bore and proportioned such that the piston is adapted to reciprocate through said O-ring in piston-sealing relation therewith so that thedistance along said second bore between said O-ring and said first bore comprises the pump cylinder, removable plug means in the enlarged portions of the second bore to retain said first O-ring in position, the first of said bores comprising inlet and outlet ports for said pump, a check valve -disposed at the shoulder in leach port on opposite sides of said second bore, sa'id valves comprising second and 'third' O-rings of resilient material one disposed against the shoulder in each lsaid port, vsecond and third removable plug means in Vthe -enlarged portions of said iirst bore 'to retain said second and third O-rings in position, a ball proportioned to seat in the aperture of each of said second and third O-rings, and means urging each ball against its associated O-ring to close the valve.

12. An injector pump including a cylinder block having a bore therein, O-rings of resilient material fixed at opposite ends of said boreto Vform a cylinder therebetween, a piston disposed to reciprocate in said cylinder and proportioned to pass through both O-rings in continuous sealed lrelation therewith, an O-ring of resilient material axed to the midsection of the piston so as to be carried thereby in sealed relation to the cylinder wall, an inlet vport and an outlet port formed in said cylinder block and opening into said cylinder, said port openings lying in 'the same plane transverse to the axis of the cylinder and being spaced from one end of said cylinder by a distance exceeding the thickness of the O-ring carried by said piston, additional inlet and outlet ports formed in said cylinder block and opening into said cylinder, said last-named port openings lying in a common plane transverse to said axis and being spaced from the other end of said cylinder by a distance exceeding the thickness of the O-ring carried by said piston, a check valve :in each inlet port opening toward the cylinder, and a check valve in each outlet port closing toward said cylinder.

13. In a pump, a cylinder having top and bottom ends, a piston disposed within the cylinder and adapted to reciprocate therein, means for coupling said piston to a source of driving power, an inlet port communicating with the cylinder and spaced away from said top end, an inlet valve disposed in said port and opening toward the cylinder, an outlet port communicating with the top end ot' the cylinder and a normally closed outlet valve disposed in said outlet port .and opening out of the cylinder, said outlet valve comprising a ball, an annular seat and spring means urging said ball against the seat, said seat comprising an O-ring of resilient material having a central aperture of diameter slightly smaller than that of the head of said piston so that the piston head is scalable in said O-ring, said piston and O-ring being centered on a common axis, the piston head being so shaped with respect to said ball and said O-ring being so proportioned with respect to said ball that at one phase of the piston stroke the piston head is sealed in said O-ring when said outlet valve is closed.

14. A pump according to claim 13 in which said means for coupling the piston to a source of driving power includes means for preselecting the pump capacity which comprises means for adjusting the proportion of the length of the part of the piston stroke which occurs be tween said O-ring and the bottom of the stroke to the length of the total piston stroke.

l5. A pump according to claim 13 in which said means for coupling said piston to a source of driving power includes adjustable means for preselecting the pump capacity which comprises means for adjusting the distance between the head of the piston and the top end of the cylinder when the piston is at the bottom of its stroke, while maintaining the total length of the piston stroke constant.

16. ln an injector pump of precision type including a cylinder, a piston disposed to reciprocate therein, a driving member movable in an orbit around a center of rotation, a bearingless piston rod connected to said piston to drive the same, said piston rod comprising a length of exible resilient wire-like material so proportioned as to provide driving strength in compression and tension suicient to actuate the piston in its pumping stroke in either direction, said rod being rigidly secured at one `12 end to the piston and rigidly secured at the other end to said 'driving member, said driving member comprising a threaded stud having one end to which said flexible piston rod is rigidly secured, and a boss eccentrically movable around said .center of rotation `and having a threaded hole in which said stud is engageable whereby rotation of said piston, said rod and said stud provides adjustment of the distance between the head of thepiston and said center of rotation so as to change the position of the `piston in said cylinder with constant stroke length.

'17. An Vinjector pump of adjustable capacity, which includes a cylinder having a cylinder head, an inlet valve ported in said cylinder, a piston disposed to reciprocate in said cylinder, an opening through said cylinder head adapted .to receive the piston, means for sealing the piston in the cylinder head, an outlet valve communicating with said opening, the travel path of the piston being such that in approaching the top of its stroke the piston is adapted to pass through said opening in sealed relation to the cylinder head, and means for driving the piston in reciprocating movement in said cylinder with constant stroke length which comprises a driving member, a piston rOd connected at one end to the piston, coupling means movably connected to said driving member and secured to the other end of said piston rod, and adjusting vmeans for changing the length of said coupling means so as eiectively to adjust the length of said connecting rod, whereby to adjust the position or" the travel path of the piston in the cylinder kand thereby to adjust the pump capacity per stroke. Y

18. An injector pump includes a cylinder having of adjustable capacity, which a cylinder head, an inlet Valve ported in said cylinder, a piston disposed to reciprocate in said cylinder, an opening through said cylinder head adapted to receive the piston, means for sealing the piston in the cylinder head, an outlet valve communicating with said opening, the travel path of the piston being such that in approaching the 'top of its stroke the piston is adapted to pass through said opening in sealed relation to the cylinder head and 'thus to pass out of the cylinder, and means for driving the piston in reciprocating movement in said cylinder with constant stroke length which includes adjustable means for changing the Vportion of the total length of the piston stroke which occurs within the cylinder, whereby to adjust the pump capacity per stroke.

19. In a pump, a cylinder, a piston adapted to reciprocate therein, said piston having a piston head, an inlet valve disposed in a port opening into the cylinder and an outlet valve disposed in a port opening out ofthe cylinder, said outlet valve substantially constituting the cylinder lhead and having a Vseat comprising an O-ring of resilient material disposed within the travel path of the piston and a ball closing said seat, said seat being formed with a central opening large enough to pass the piston head in sealed Vrelation therewith, said piston'head being circular and concaved to iit said ball, and means for extending the piston stro-ke so that as the piston approaches the top of its forward stroke the piston head is adaptedto receive said ball in its concave portion and mechanically to raise said ball from its seat and, on the return stroke, to release the ball in engagement with 'its seat while the seal between said piston head and said O-ring is maintained.

20. An injector pump of adjustable capacity, which includes a cylinder, a piston having a piste-n head and being disposed to reciprocate in the cylinder over a variable stroke path and with constant stroke length, inlet and outlet valves for said cylinder, said outlet valve being ported into said cylinder at a position along said path intermediate the extremes of said stroke length such that the pump capacity is a function of the distance along said path between the outlet valve port and the position of the piston head at one extreme of its stroke, and means for driving said piston with constant stroke length including a driven rotating member, attachment means pivoted eccentrically on said member, and a connecting rod interconnecting said piston and said attachment means, said connecting rod comprising a length of hardened, normally straight, exible resilient wire secured at one end to said piston, and means secured to the other end of said wire, securable to said attachment means and adjustable lengthwise in respect to said attachment means, whereby to adjust the position of the piston path in respect to the outlet valve and thereby the pump capacity per stroke.

References Cited in the le of this patent UNITED STATES PATENTS Scott Feb. 9, Schaumann Jan. 12, Coon Nov. 4, Neyer Mar. 3, Corneil Oct. 30, Born Ian. 21,

FOREIGN PATENTS Switzerland Ian. 2,

UNITED STATES PATENT OFFICE CERTIFICATE oF CORRECTION PatentA No 2,9l6q998 December 1.5il 1959 Carl A Miller It is hereby'cerpified Ripe error appears in the printed specification of' the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 91l line 58 for "another" read a second same line 58K for "a second read another same column 9, llne` 64g for "values" read valves Signed and sealed this 20th day of September 196C.

f SEAL) -Attest KARL I-L AXLINE ROBERT C. WATSON Attesting Officer rCommissioner of Patents 

